1. Field of the Invention
The present invention relates to a photographic system having the function of correcting blurring of an image caused by vibrations or the like, i.e., commonly called the vibration-proof function. More particularly, the present invention pertains to an image stabilizing device for use in a photographic system which enables the size and weight of a blurring correcting movable lens group to be reduced. This, in time, prevents a reduction in the optical performance of the photographic system, which would occur when the movable lens group is moved in, for example, a direction perpendicular to an optical axis to correct blurring. An improved controllability of an actuator also is assured.
2. Description of the Related Art
When pictures are taken on a moving object, such as a running vehicle or an airplane, vibrations of the moving object are transmitted to a photographic system, causing images to be blurred. The degree of blurring occurring in the images also will increase, for example, when the focal length of the photographic system increases.
The present applicant has already proposed photographic systems having the vibration-proof function for preventing blurring of an image in, for example, Japanese Patent Laid-Open Nos. 133119/1988, 229425/1988, and 201623/1988.
In such photographic systems, if the optical axis of a camera lens system, for example, deviates due to vibrations occurring in the camera, the deviation of images caused by the deviation of the lens system will be calculated by an acceleration sensor or the like incorporated in the camera. On the basis of the output of the acceleration sensor, part of the lens groups of the photographic system which is disposed closest to an image surface is decentered in, for example, a direction perpendicular to the optical axis, i.e., the decentering is in a direction so that deviation of the image will be cancelled.
This decentering operation provides for excellent still images.
FIGS. 7 (A), (B) and (C) show the essential parts of a prior art photographic system with a vibration-proof function, such as is disclosed by Japanese Patent Laid-Open No. 201623/1988. The photographic system contains an afocal lens group 41, which is composed of a converging lens sub-group 41a and a diverging lens sub-group 41b, and a converging movable lens group 42.
FIG. 7 (A) shows a normal state, and FIG. 7 (B) shows a state in which an image on the optical axis is deviated from a center 46 of an image surface 45 due to vibrations or the like.
Blurring of the image is corrected and a still image is thereby obtained by decentering the movable lens group 42 in, for example, a direction perpendicular to the optical axis by means of an actuator 43 which is operated on the basis of an output signal from an acceleration sensor 44, as shown in FIG. 7 (C).
In a mechanism for eliminating blurring of an image by vibrating part of the lens group in a photographic system so as to provide still images, a blurring correcting movable lens group generally must contain a lesser number of lenses and be, therefore, small and light-weight. Furthermore, the degree of aberration generated by decentering the movable lens in, for example, the direction perpendicular to the optical axis must be low. Hence, a degree of reduction in the optical performance must be low. Also, the structure of the blur eliminating mechanism must be simple.
However, it normally is very difficult to provide a photographic system that satisfies all of the aforementioned conditions. In particular, decentering of the lens group which provides part of the refractive power of the photographic system will reduce the optical performance of the photographic system greatly, making it impossible to obtain excellent images. Related applications include the commonly-owned, copending U.S. application Ser. Nos. 07/261,231, and 07/417,429.